IR tracking system

In the last few days we are trying to do some experiment using Isadora Eyes motion tracking system.

The problem found is the follow: on the stage we have some white doors on wheel and we project on those a video. No light coming from the front of the stage, just blu led bars backlight on the backdrop. Eyes can recognize the white doors (we have try also the Chorma trick), but, when we move it, the video start to follow the doors with quite big delay and shifting.

On the forum we read something about IR tracking system, but we don't know if is the best solution to the problem and how to manage this tecnology. Which kind of IR camera we have to use? More than one? How far from the stage we have to position it? Which kind of IR sensor and how many we have to place on the doors? Or, conversely, we have to lighting the stage with lot of IR light and work in negative image?

To do good IR tracking you need first clean the area of IR light, and your image. You need to block all incandescent lamps from outputting IR light. Roscolux 1995 will help with this.

Next is to make sure your camera has an IR bandpass filter installed. you also have to match this with the sensitivity of the camera (different sensors get different IR frequency better or worse) midwest optic has a full range of IR pass filters and adaptors to make it fit your camera.

Also you camera has to be either ready for IR or have the IR blocking filter removed manually, as well as having total manual control over all settings.

Next you need a good IR light source- depending on what your setup this can change a lot, there are panels and floods etc.

Now with a clean setup you can begin. It is a good idea to look at how you can get the most contrast between what you want to track and the surrounding. This is often difficult as high levels of IR illumination also show up as white. One method that works well is to light the moving subject from behind with an array of IR LEDS. This gives you a blown out image but with a lot of contrast, the moving subject blocks the light and gives enough contrast for good tracking.

Beware some textiles reflect a lot of IR light, it is worth checking all the costumes to make sure they will work in the tracking.